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Date: Tue, 26 Oct 2021 20:00:37 +0800
From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: Yue Hu <huyue2@yulong.com>
Subject: Re: [RFC PATCH 1/2] erofs-utils: support tail-packing inline
 compressed data
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 <9adbee63d0bfb18ec3f8de66d196f8ffee483226.1635162978.git.huyue2@yulong.com>
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 <linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org>

Hi Yue,

On Mon, Oct 25, 2021 at 08:30:43PM +0800, Yue Hu wrote:
> Currently, we only support tail-end inline data for uncompressed
> files, let's support it as well for compressed files.
> 
> The idea is from Xiang.
> 
> Signed-off-by: Yue Hu <huyue2@yulong.com>

The patch roughly looks good to me. I'll play with it this week later.

Some comments inline:

> ---
>  include/erofs/internal.h |  2 ++
>  include/erofs_fs.h       |  6 +++-
>  lib/compress.c           | 74 ++++++++++++++++++++++++++++++++--------
>  lib/compressor.c         |  9 ++---
>  lib/decompress.c         |  4 +++
>  lib/inode.c              | 50 +++++++++++++++------------
>  mkfs/main.c              |  6 ++++
>  7 files changed, 109 insertions(+), 42 deletions(-)
> 
> diff --git a/include/erofs/internal.h b/include/erofs/internal.h
> index da7be56..42ae1ed 100644
> --- a/include/erofs/internal.h
> +++ b/include/erofs/internal.h
> @@ -109,6 +109,7 @@ static inline void erofs_sb_clear_##name(void) \
>  EROFS_FEATURE_FUNCS(lz4_0padding, incompat, INCOMPAT_LZ4_0PADDING)
>  EROFS_FEATURE_FUNCS(compr_cfgs, incompat, INCOMPAT_COMPR_CFGS)
>  EROFS_FEATURE_FUNCS(big_pcluster, incompat, INCOMPAT_BIG_PCLUSTER)
> +EROFS_FEATURE_FUNCS(tailpacking, incompat, INCOMPAT_TAILPACKING)
>  EROFS_FEATURE_FUNCS(sb_chksum, compat, COMPAT_SB_CHKSUM)
>  
>  #define EROFS_I_EA_INITED	(1 << 0)
> @@ -148,6 +149,7 @@ struct erofs_inode {
>  	unsigned char inode_isize;
>  	/* inline tail-end packing size */
>  	unsigned short idata_size;
> +	bool idata_raw;
>  
>  	unsigned int xattr_isize;
>  	unsigned int extent_isize;
> diff --git a/include/erofs_fs.h b/include/erofs_fs.h
> index 18fc182..7700b27 100644
> --- a/include/erofs_fs.h
> +++ b/include/erofs_fs.h
> @@ -22,10 +22,12 @@
>  #define EROFS_FEATURE_INCOMPAT_LZ4_0PADDING	0x00000001
>  #define EROFS_FEATURE_INCOMPAT_COMPR_CFGS	0x00000002
>  #define EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER	0x00000002
> +#define EROFS_FEATURE_INCOMPAT_TAILPACKING	0x00000004
>  #define EROFS_ALL_FEATURE_INCOMPAT		\
>  	(EROFS_FEATURE_INCOMPAT_LZ4_0PADDING | \
>  	 EROFS_FEATURE_INCOMPAT_COMPR_CFGS | \
> -	 EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER)
> +	 EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER | \
> +	 EROFS_FEATURE_INCOMPAT_TAILPACKING)
>  
>  #define EROFS_SB_EXTSLOT_SIZE	16
>  
> @@ -230,10 +232,12 @@ struct z_erofs_lz4_cfgs {
>   *                                  (4B) + 2B + (4B) if compacted 2B is on.
>   * bit 1 : HEAD1 big pcluster (0 - off; 1 - on)
>   * bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
> + * bit 3 : inline (un)compressed data
>   */
>  #define Z_EROFS_ADVISE_COMPACTED_2B		0x0001
>  #define Z_EROFS_ADVISE_BIG_PCLUSTER_1		0x0002
>  #define Z_EROFS_ADVISE_BIG_PCLUSTER_2		0x0004
> +#define Z_EROFS_ADVISE_TAILPACKING		0x0008
>  
>  struct z_erofs_map_header {
>  	__le32	h_reserved1;
> diff --git a/lib/compress.c b/lib/compress.c
> index 2093bfd..c19f554 100644
> --- a/lib/compress.c
> +++ b/lib/compress.c
> @@ -159,6 +159,18 @@ static unsigned int z_erofs_get_max_pclusterblks(struct erofs_inode *inode)
>  	return cfg.c_physical_clusterblks;
>  }
>  
> +static int z_erofs_fill_inline_data(struct erofs_inode *inode, char *data,
> +				    unsigned int len, bool raw)
> +{
> +	inode->idata_raw = raw;
> +	inode->idata_size = len;
> +	inode->idata = malloc(inode->idata_size);
> +	if (!inode->idata)
> +		return -ENOMEM;
> +	memcpy(inode->idata, data, inode->idata_size);
> +	return 0;
> +}
> +
>  static int vle_compress_one(struct erofs_inode *inode,
>  			    struct z_erofs_vle_compress_ctx *ctx,
>  			    bool final)
> @@ -169,15 +181,19 @@ static int vle_compress_one(struct erofs_inode *inode,
>  	int ret;
>  	static char dstbuf[EROFS_CONFIG_COMPR_MAX_SZ + EROFS_BLKSIZ];
>  	char *const dst = dstbuf + EROFS_BLKSIZ;
> +	bool tail_pcluster = false;
>  
>  	while (len) {
> -		const unsigned int pclustersize =
> +		unsigned int pclustersize =
>  			z_erofs_get_max_pclusterblks(inode) * EROFS_BLKSIZ;
>  		bool raw;
>  
> -		if (len <= pclustersize) {
> +		if (!tail_pcluster && len <= pclustersize) {
>  			if (final) {
> -				if (len <= EROFS_BLKSIZ)
> +				if (erofs_sb_has_tailpacking()) {
> +					tail_pcluster = true;
> +					pclustersize = EROFS_BLKSIZ;

Not quite sure if such condition can be trigged for many times...

Think about it. If the original pclustersize == 16 * EROFS_BLKSIZ, so we
could have at least 16 new pclustersize == EROFS_BLKSIZ then?

But only the last pclustersize == EROFS_BLKSIZ can be inlined...

> +				} else if (len <= EROFS_BLKSIZ)
>  					goto nocompression;
>  			} else {
>  				break;
> @@ -194,6 +210,17 @@ static int vle_compress_one(struct erofs_inode *inode,
>  					  inode->i_srcpath,
>  					  erofs_strerror(ret));
>  			}
> +			if (tail_pcluster && len < EROFS_BLKSIZ) {
> +				ret = z_erofs_fill_inline_data(inode,
> +					(char *)(ctx->queue + ctx->head), len,
> +					true);
> +				if (ret)
> +					return ret;
> +				count = len;
> +				raw = true;
> +				ctx->compressedblks = 1;
> +				goto add_head;
> +			}
>  nocompression:
>  			ret = write_uncompressed_extent(ctx, &len, dst);
>  			if (ret < 0)
> @@ -202,6 +229,16 @@ nocompression:
>  			ctx->compressedblks = 1;
>  			raw = true;
>  		} else {
> +			if (tail_pcluster && ret < EROFS_BLKSIZ &&
> +			    !(len - count)) {
> +				ret = z_erofs_fill_inline_data(inode, dst, ret,
> +							       false);
> +				if (ret)
> +					return ret;
> +				raw = false;
> +				ctx->compressedblks = 1;
> +				goto add_head;
> +			}
>  			const unsigned int tailused = ret & (EROFS_BLKSIZ - 1);
>  			const unsigned int padding =
>  				erofs_sb_has_lz4_0padding() && tailused ?
> @@ -226,11 +263,13 @@ nocompression:
>  			raw = false;
>  		}
>  
> +add_head:
>  		ctx->head += count;
>  		/* write compression indexes for this pcluster */
>  		vle_write_indexes(ctx, count, raw);
>  
> -		ctx->blkaddr += ctx->compressedblks;
> +		if (!inode->idata_size)
> +			ctx->blkaddr += ctx->compressedblks;
>  		len -= count;
>  
>  		if (!final && ctx->head >= EROFS_CONFIG_COMPR_MAX_SZ) {
> @@ -475,7 +514,7 @@ int erofs_write_compressed_file(struct erofs_inode *inode)
>  	fd = open(inode->i_srcpath, O_RDONLY | O_BINARY);
>  	if (fd < 0) {
>  		ret = -errno;
> -		goto err_free;
> +		goto err_free_meta;
>  	}
>  
>  	/* allocate main data buffer */
> @@ -530,16 +569,19 @@ int erofs_write_compressed_file(struct erofs_inode *inode)
>  			goto err_bdrop;
>  	}
>  
> +	inode->idata_size = 0;
> +
>  	/* do the final round */
>  	ret = vle_compress_one(inode, &ctx, true);
>  	if (ret)
> -		goto err_bdrop;
> +		goto err_free_id;
>  
>  	/* fall back to no compression mode */
>  	compressed_blocks = ctx.blkaddr - blkaddr;
> -	if (compressed_blocks >= BLK_ROUND_UP(inode->i_size)) {
> +	if (compressed_blocks >= BLK_ROUND_UP(inode->i_size) -
> +	    (inode->idata_size ? 1 : 0) ) {
>  		ret = -ENOSPC;
> -		goto err_bdrop;
> +		goto err_free_id;
>  	}
>  
>  	vle_write_indexes_final(&ctx);
> @@ -553,12 +595,11 @@ int erofs_write_compressed_file(struct erofs_inode *inode)
>  		   inode->i_srcpath, (unsigned long long)inode->i_size,
>  		   compressed_blocks);
>  
> -	/*
> -	 * TODO: need to move erofs_bdrop to erofs_write_tail_end
> -	 *       when both mkfs & kernel support compression inline.
> -	 */
> -	erofs_bdrop(bh, false);
> -	inode->idata_size = 0;
> +	if (inode->idata_size)
> +		inode->bh_data = bh;
> +	else
> +		erofs_bdrop(bh, false);
> +
>  	inode->u.i_blocks = compressed_blocks;
>  
>  	legacymetasize = ctx.metacur - compressmeta;
> @@ -573,11 +614,14 @@ int erofs_write_compressed_file(struct erofs_inode *inode)
>  	inode->compressmeta = compressmeta;
>  	return 0;
>  
> +err_free_id:
> +	if (inode->idata)
> +		free(inode->idata);
>  err_bdrop:
>  	erofs_bdrop(bh, true);	/* revoke buffer */
>  err_close:
>  	close(fd);
> -err_free:
> +err_free_meta:
>  	free(compressmeta);
>  	return ret;
>  }
> diff --git a/lib/compressor.c b/lib/compressor.c
> index 8836e0c..26189b6 100644
> --- a/lib/compressor.c
> +++ b/lib/compressor.c
> @@ -28,7 +28,7 @@ int erofs_compress_destsize(struct erofs_compress *c,
>  			    void *dst,
>  			    unsigned int dstsize)
>  {
> -	unsigned uncompressed_size;
> +	unsigned compressed_size;
>  	int ret;
>  
>  	DBG_BUGON(!c->alg);
> @@ -41,9 +41,10 @@ int erofs_compress_destsize(struct erofs_compress *c,
>  		return ret;
>  
>  	/* check if there is enough gains to compress */
> -	uncompressed_size = *srcsize;
> -	if (roundup(ret, EROFS_BLKSIZ) >= uncompressed_size *
> -	    c->compress_threshold / 100)
> +	compressed_size = *srcsize <= EROFS_BLKSIZ ? ret :
> +			  roundup(ret, EROFS_BLKSIZ);
> +
> +	if (*srcsize <= compressed_size * c->compress_threshold / 100)
>  		return -EAGAIN;
>  	return ret;
>  }
> diff --git a/lib/decompress.c b/lib/decompress.c
> index 490c4bc..0b6678d 100644
> --- a/lib/decompress.c
> +++ b/lib/decompress.c
> @@ -9,6 +9,7 @@
>  
>  #include "erofs/decompress.h"
>  #include "erofs/err.h"
> +#include "erofs/print.h"
>  
>  #ifdef LZ4_ENABLED
>  #include <lz4.h>
> @@ -50,6 +51,9 @@ static int z_erofs_decompress_lz4(struct z_erofs_decompress_req *rq)
>  					  rq->decodedlength);
>  
>  	if (ret != (int)rq->decodedlength) {
> +		erofs_err("failed to %s decompress %d in[%u, %u] out[%u]",
> +			  rq->partial_decoding ? "partial" : "full",
> +			  ret, rq->inputsize, inputmargin, rq->decodedlength);
>  		ret = -EIO;
>  		goto out;
>  	}
> diff --git a/lib/inode.c b/lib/inode.c
> index 787e5b4..1c08608 100644
> --- a/lib/inode.c
> +++ b/lib/inode.c
> @@ -521,9 +521,6 @@ int erofs_prepare_tail_block(struct erofs_inode *inode)
>  	struct erofs_buffer_head *bh;
>  	int ret;
>  
> -	if (!inode->idata_size)
> -		return 0;
> -
>  	bh = inode->bh_data;
>  	if (!bh) {
>  		bh = erofs_balloc(DATA, EROFS_BLKSIZ, 0, 0);
> @@ -557,26 +554,21 @@ int erofs_prepare_inode_buffer(struct erofs_inode *inode)
>  		inodesize = Z_EROFS_VLE_EXTENT_ALIGN(inodesize) +
>  			    inode->extent_isize;
>  
> -	if (is_inode_layout_compression(inode))
> -		goto noinline;
> -
> -	/*
> -	 * if the file size is block-aligned for uncompressed files,
> -	 * should use EROFS_INODE_FLAT_PLAIN data mapping mode.
> -	 */
>  	if (!inode->idata_size)
> -		inode->datalayout = EROFS_INODE_FLAT_PLAIN;
> +		goto noinline;
>  
>  	bh = erofs_balloc(INODE, inodesize, 0, inode->idata_size);
>  	if (bh == ERR_PTR(-ENOSPC)) {
>  		int ret;
>  
> -		inode->datalayout = EROFS_INODE_FLAT_PLAIN;
> -noinline:
>  		/* expend an extra block for tail-end data */
>  		ret = erofs_prepare_tail_block(inode);
>  		if (ret)
>  			return ret;
> +noinline:
> +		if (!is_inode_layout_compression(inode))
> +			inode->datalayout = EROFS_INODE_FLAT_PLAIN;
> +
>  		bh = erofs_balloc(INODE, inodesize, 0, 0);
>  		if (IS_ERR(bh))
>  			return PTR_ERR(bh);
> @@ -584,7 +576,16 @@ noinline:
>  	} else if (IS_ERR(bh)) {
>  		return PTR_ERR(bh);
>  	} else if (inode->idata_size) {
> -		inode->datalayout = EROFS_INODE_FLAT_INLINE;
> +		if (is_inode_layout_compression(inode)) {
> +			struct z_erofs_map_header *h = inode->compressmeta;
> +			h->h_advise |= Z_EROFS_ADVISE_TAILPACKING;
> +			erofs_dbg("%s: inline %scompressed data (%u bytes)",
> +				  inode->i_srcpath,
> +				  inode->idata_raw ? "un" : "",
> +				  inode->idata_size);
> +		} else {
> +			inode->datalayout = EROFS_INODE_FLAT_INLINE;
> +		}
>  
>  		/* allocate inline buffer */
>  		ibh = erofs_battach(bh, META, inode->idata_size);
> @@ -640,20 +641,25 @@ int erofs_write_tail_end(struct erofs_inode *inode)
>  		ibh->op = &erofs_write_inline_bhops;
>  	} else {
>  		int ret;
> -		erofs_off_t pos;
> +		erofs_off_t pos, pos0;
> +		const unsigned short padding = EROFS_BLKSIZ - inode->idata_size;
>  
>  		erofs_mapbh(bh->block);
>  		pos = erofs_btell(bh, true) - EROFS_BLKSIZ;
> +		pos0 = pos + inode->idata_size;
> +
> +		if (is_inode_layout_compression(inode) &&
> +		    erofs_sb_has_lz4_0padding() && !inode->idata_raw) {
> +			pos0 = pos;
> +			pos += padding;
> +		}

I'd suggest don't use 0padding but record compressed_sized for
tail-packing pcluster in the map header.... (need 2 bytes to record)

Thanks,
Gao Xiang

>  		ret = dev_write(inode->idata, pos, inode->idata_size);
>  		if (ret)
>  			return ret;
> -		if (inode->idata_size < EROFS_BLKSIZ) {
> -			ret = dev_fillzero(pos + inode->idata_size,
> -					   EROFS_BLKSIZ - inode->idata_size,
> -					   false);
> -			if (ret)
> -				return ret;
> -		}
> +		ret = dev_fillzero(pos0, padding, false);
> +		if (ret)
> +			return ret;
> +
>  		inode->idata_size = 0;
>  		free(inode->idata);
>  		inode->idata = NULL;
> diff --git a/mkfs/main.c b/mkfs/main.c
> index e476189..7dd29df 100644
> --- a/mkfs/main.c
> +++ b/mkfs/main.c
> @@ -48,6 +48,7 @@ static struct option long_options[] = {
>  	{"product-out", required_argument, NULL, 11},
>  	{"fs-config-file", required_argument, NULL, 12},
>  #endif
> +	{"inline", no_argument, NULL, 13},
>  	{0, 0, 0, 0},
>  };
>  
> @@ -87,6 +88,7 @@ static void usage(void)
>  	      " --all-root            make all files owned by root\n"
>  	      " --help                display this help and exit\n"
>  	      " --max-extent-bytes=#  set maximum decompressed extent size # in bytes\n"
> +	      " --inline              tail-packing inline compressed data\n"
>  #ifndef NDEBUG
>  	      " --random-pclusterblks randomize pclusterblks for big pcluster (debugging only)\n"
>  #endif
> @@ -304,6 +306,10 @@ static int mkfs_parse_options_cfg(int argc, char *argv[])
>  			}
>  			cfg.c_physical_clusterblks = i / EROFS_BLKSIZ;
>  			break;
> +		case 13:
> +			erofs_sb_set_tailpacking();
> +			erofs_warn("EXPERIMENTAL compression inline feature in use. Use at your own risk!");
> +			break;
>  
>  		case 1:
>  			usage();
> -- 
> 2.29.0
> 
>